To HLV or not to HLV?`
The alt.space community is split on several issues, but one that I keep seeing pop up is whether or not NASA should be developing the HLV. Recently there were two articles posted to space.com which attempted to argue each side of the debate. First up was John Strickland who wrote an article about the kinds of missions which could only be accomplished by launching very large payloads on HLV's. A few days later, Edward Wright wrote a response which described how much more expensive it would be to launch large payloads on one HLV than it would be to launch multiple smaller payloads on EELV's.
The primary argument in favor of the HLV is that there are some missions which just cannot be accomplished without launching very large integrated payloads. Mr. Strickland outlines some of these missions in his article (linked to above). Others, like Robert Zubrin, also see HLV as a means to avoid doing time consuming on-orbit assembly, and a way to avoid lengthy delays in missions if one or more components of a multiple launch architecture are delayed or destroyed.
The main argument against the HLV is that there is insufficient demand for it. NASA's expected flight rate will be far too low to see any practical return on the massive amount of R&D required to develop the booster. The fact that NASA would rather go with yet another proprietary booster than with existing EELV's is also regarded as anticompetive; depriving struggling launch providers of a significant number of NASA payloads. The new ESAS, as it is currently formulated, is seen as a waste of resources that could be better spent if NASA simply designed its architecture to be launched on EELV's.
Each side raises valid points, but they each argue as if it's an all or nothing proposition. Either NASA designs its architecture so that all of the components are launched on HLV's or everything on EELV's. Manned flights beyond LEO are going to require lots of mass delivered to orbit and it's very possible that this mass could be delivered by both EELV's and HLV's. As far as the ESAS is concerned, I think that NASA would rather go with an HLV than multiple EELV's for their early missions because they have experience doing it that way, and they are fairly certain they can do it again. In the current risk adverse climate at NASA, practicality seems to be winning out over innovation.
For example, within the next five or six years, NASA could begin sending small unmanned decent stages to the moon loaded with ISRU equipment, solar panels, telepresence robots, spare parts, etc. This would allow them to begin testing out and refining technology that the manned missions will eventually rely upon as well as checking out landing sites and setting up small amounts of infrastructure. I believe that there are already robotic landers (to be launched on EELV's) in the current ESAS. All that I am proposing is a slight expansion of this aspect of the architecture to support delivery of smaller components to the lunar surface independent of the large integrated structures. This is just one example of how NASA could take advantage of the availability of the EELV class of launch vehicles in their architecture. I'm sure that there are many others.